I just jump-started my fiancee's '89 Honda Accord with my '03 Z.
It's not dangerous, you just need to hook it up correctly:
Hook them up in numerical order...
Booster car (my Z):
1. red to +
2. black to -
Dead car (Accord):
3. red to +
4. black to ground
* Don't hook the black to the negative battery terminal. Ground the negative to a bare-metal bolt somewhere on the body. If you get a spark, it's a good connection.
Keep the Booster car running, and all should work out just fine.
RoadRagerInTherapy / '06 Black G35 Sedan M6 / '03 Daytona Blue 350Z Track (written off - R.I.P.) / Toronto, Ontario, Canada